Lightweight rail

Lightweight rail
is railway
adapted to the weight of extra light goods to be transported. A
high-speed
train is for passengers, implying only 6-8 tonnes/wagon, and
yet the traditional railway concept for at least 100 tonnes/wagon
is normally used. Lightweight rail implies designing the train on
the basis of this low required weight and trying to exploit the
benefits then obtainable.

The term Lightweight
rail should not be confused with the
common term light
rail, which only partly implies low weight, but primarily
implies the ability to merge with city traffic, in contrast to
heavy rail,
which requires a separate right-of-way.
Light rail has only partly explored the potentials of low weight,
but enough to be able to negotiate the grades in sloping cities and
other terrains it has to adapt to.

Can trains be light?

The minimum weight for trains running on the
ground was demonstrated in February 2007 when a train was derailed
by snow masses on a Norwegian mountain line. The train —
called a Signature train — consisted of motorized wagons,
each with 72 seats and weighing 54 tonnes. A local train expert
told the media that he had warned against using such a light train,
as it could slide like a snowboard and derail. A heavier
locomotive,
which could push an efficient snow plow, should be used in front.

In warmer climates, where snow masses may be
disregarded, trains must still be built to survive collisions with
cattle and other large animals, as well as crossing road vehicles.
If the track were lifted 4-5 meters
above the ground, resting on pillars, both snow mass disturbance
and collision danger would be virtually eliminated, so now
lightweight technology could be employed. A positive feedback is
encountered here: Rail elevation enables light trains, and light
trains are easy to elevate above the ground. Such positive feedback
situations can create quantum leaps in technology, and this effect
seems to be effective here.

An empty lightweight wagon for 70 passengers could
weigh only 5 tonnes, against 40 tonnes for the railway wagon. If
the total weight is used, with motorized bogies, it becomes 6.4
tonnes, but this weight can be compared with a 40-tonne wagon among
6-7 such wagons pulled by an 80-tonne locomotive. In both cases the
beamway train has only 1/8 of the weight. The 70 passengers in the
railway train have a 25 meter long wagon, while the 70 in the
beamway train have 16-18 meters, so it may be more correct to use
the ratio 1/6. If the weight of the passengers equals the weight of
a light wagon, the ratio becomes 2/7.

The strongest forces at the safe altitudes
would be those from the wind and the passengers. Special
circumstances like unusual transport or construction activities
could impose obstacles, but they are easy to detect (by ultrasound
echo or radar) and
require no recognition capability — just automatic braking.
This simplification of the environment makes it possible to use
driverless and computer-controlled trains. Another advantage of the
elevated track is that the power line can easily be built into it,
without being a danger for people or animals, and without being
disturbed by rain or snow.

Environmental implications

The advantages of reduced weight become evident in
three areas:

Reduction
of energy consumption and exerted forces.
Energy losses caused by rolling friction
are reduced when the train weight is reduced. But at higher speeds
the air
resistance becomes more important, and this is independent of
the train weight, depending primarily upon the cross-section area
of the train. A lighter train exerts smaller forces during braking
and turning, and this will in return enable lighter and cheaper
track designs.

Openness for crossing traffic under an
elevated railway. A conventional railway will form a barrier
along its path. It may have some crossings for roads, but will
still be a barrier for the local population or animal life. An
elevated track with 2x2 meter openings will enable people and most
animals to pass and feel unhindered. 4-5 meter high and 5+ meter
wide openings will enable frequent road and street crossings.

Elevated rail designs

A conventional railway track is so wide that
the train can easily balance on top of it, and this works fine on a
flat surface. But when the track is to be elevated on top of
pillars, it should be designed like a stiff beam. This means: It
should be thick vertically, but narrow. A wide beam will be heavy,
expensive, and often annoyingly overshadowing. The train should not
try to balance on top of a wide beam, but achieve stability by
wrapping partly around the upper part of a narrower beam. We now
have a straddling monorail,
also called the Alweg
type train.

The train itself can be lightweight, but the track
— normally a concrete beam resting on concrete pillars —
has some problems:

The beam becomes a
barrier between the train and the ground below, so that the train
cannot have an elevator for arriving and departing passengers, but
needs expensive raised stations at all stops — unless the
railway has a reserved area allowing the track to go low at
stations. (The elevator also functions as a sluice mechanism
including a weight, so that train overloading can be automatically
prevented.)

Having trains on the top makes it
difficult for the track to take long jumps by having the steel
beam suspended under a catenary
cable — like an ordinary suspension
bridge is suspended under two.

So we let the train hang under a steel beam,
and now we have a suspended monorail, also called a SAFEGE-type
monorail, or a beamway.

Beamway
train designs with elevator

Suspended beamway trains

Steel beams held up by metal poles give a
lightweight track — at least in terms of volume and visual
disturbance, and when the poles can be 30-40 meters apart, the
train can act as a tram or bus in a dense city. It can follow a
road just above it — also on bridges — and may get a
quite straight route even if the road curves somewhat back and
forth — by taking shortcuts over sidewalks, fences, gardens
etc.. It may not seem plausible that real trains can run on long
and not very stiff beams, but a long train will have much of its
weight in the strong track parts near poles, and the train parts in
the weak beam parts midway between poles, need not strain seriously
if the train has some stiffness — preferably a dynamically
adjustable one.

Cross
section of a beamway beam. The power rail (orange in the middle) is
mounted in plastic.

A beamway's bogies
run inside the hollow beam, so the wheels always have a dry and
clean path. The exposed environment of the straddling train, on the
other hand, can collect some snow — enough to prevent
high-speed operation. And such a top surface is likely to invite
birds for a rest with a view — and a massacre.

(A third suspension alternative is to let the
train ride on the side of a tall beam which can carry trains on
both sides, but then it will be difficult to avoid heavy loadings
of the wheels — which should not be small if high speed is
wanted.[1][2])
In addition to the wheels inside the beam, wheels can roll under
the bottom of the beam. If the two sets of wheels are pressed
together, hillclimbing abilities are greatly improved. Brakes which
likewise pinch the bottom of the beam, will be far more efficient
than traditional wheel brakes. When the track is a relatively
compact beam, it becomes possible to move it in various ways:

To swing it up or
sideways where it crosses e.g. a river with boat traffic

To displace one end
of a beam — for switching between two or more alternative
lines

To let the beamway
be held by floaters on the sea — even though the tides will
tilt the transition beam a little

To let a beam be
held by an elevator mechanism which can lift/lower the beam with a
train to a different altitude

To let a beam be
moved sideways on two parallel tracks which are perpendicular to
the beam — so that the beamway can scan an area for e.g.
agricultural purposes

To let the beam be held by racks standing on
the ground — for a provisional railway line

Movable
beams

A
beamway elevator

Harvesting
beamway

Movable
beamway racks

Transferable passenger cabins

When the passenger cabin is light, it becomes
feasible to make it detachable, so that it can be transferred to
other transport systems. This gives potentials for the many
flexibility advantages long reaped by container transport of cargo.
But passenger cabin transfers must be fast, and without experiences
of dangling under cranes. The beamway has unique potentials in this
respect, because its beam can lead to a position very close above
other vehicles/platforms, such as a boat deck, a flat freight wagon
on conventional railway, or a trailer-like bus. Only
centimeters/inches of lowering will be required for transferring
the cabin to the recipient, so this would hardly give the
passengers any experience of dangling under a crane.[3]

A
cabin transferred to a boat

Potentials for advanced technology

When the weight is low, it is much easier to
replace those awkward wheels with advanced levitation technology
like magnetic levitation — maglev.
Its use in a beamway beam is also simplified by factors like:

A clean
environment: no dust, debris and snow — just clean metal

No stability
problems when the train is hanging under the levitation mechanism
— which is even confined between steel walls

Smaller dimensions

The beam tolerates little loading by
levitation mechanisms along the track, but the passive coils used
by the Inductrack
system may be light enough. The interior of the beam also
facilitates another stable levitation method: Windsurfing, either
by Hovercraft-style
air pumps, or simply by sliding passively on the air cushion
obtained under airfoils after rolling on wheels up to a high enough
speed. When there is no contact between wheels and the beam,
conventional motors can't be used, and must be replaced by
alternative
propulsion — probably the linear
motor, which may be integrated in the maglev
mechanism. [4]

A
cabin for bus use

Low weight equals low capacity?

For moving large pieces of cargo, these lightweight
railways (without alternative heavyweight transport nearby) would
be unsatisfactory. But for moving people and light cargo, a
bidirectional beamway line could have less than one minute between
trains, if it were not for the irregularity introduced at stops. If
heavyweight railway entails having to do with single-track
operation instead of double-track, the long train intervals make
competition with a stream of light trains impossible —
particularly if factors like the user-friendliness of short
departure intervals, and the capacity decrease caused by a disabled
train, are taken into account. Driverless lightweight trains may be
less personnel-demanding — particularly if ticketing and
security permit trains to be fully unmanned like elevators.